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Greetings. Pictured is my 6 week old Northern Lights Auto following LST for an even canopy. I started her on a 20 hour on and 4 hour off light cycle and she is still on that timer. I use a HLG 135W LED QB light, and it is drawing 110 watts from the wall at her current setting. I checked her output with a PAR meter, and she is around 75% of her max power output.

The plant's buds are stacking up nicely as we speak. Should I adjust her light cycle or just leave it as is? I think some folks adjust the wattage and time on to save power, but 110 Watts is not a huge draw.

Leave at 20/4 or adjust? Will a reduction in light influence bud development in an auto which I think not - but not completely sure?

Flowering girls, as much light as you can. I'd max the QB and stay on schedule. You can change the light cycle, but reducing below about 18 and product will suffer. If I change in flower, its ramping up to 24/24, not the other way.

No particular reason other than thinking a change may boost her budding potential. If this is counter-productive, no reason to change unless I can see benefits.

Click to expand...

From my experience with autos, how you care for the plant and maintain the environment will determine your yield unlike photos that have to be on a 12/12 down to a 10/14 schedule. I'll probably say this wrong but because of the ruderalis they have their own internal clock that isn't dependent on light schedule. As long as you're giving them enough light, look up DLI, I can't imagine that your light cycle matters as much.

DLI in the simplest way I can explain it refers to how many umols of light in a given cycle the plant needs.

I think I have the photo light flip on my mind - and old habits die hard. Being she is 6 weeks old now, this is the point I'd normally be flipping the lights for a photo. Old dog - new tricks with the auto grow.

This Northern Lights girl is 6 weeks old and has been a good, cooperative LST plant. She is on 20/4, and I use my PAR meter to calculate her uMols which are extrapolated out to give me her DLI you mentioned @Damien50 . I'm now focusing on letting her grow vertically since I have her horizontal shape wall to wall in the 2x2. Now she can reach for the stars - or in her case a HLG QB LED.

Its obvious y'all have the experience to know that 20/4 is a good lighting pattern from start to finish. With that said, I'll leave her be for her bud development phase. First auto, but all good growing basics apply regardless. Good nutes, proper ph, well managed lighting is essential.

BTW, @Damien50, your plants in the journal you linked are gorgeous. What a grow my friend....WOW!

I think I have the photo light flip on my mind - and old habits die hard. Being she is 6 weeks old now, this is the point I'd normally be flipping the lights for a photo. Old dog - new tricks with the auto grow.

This Northern Lights girl is 6 weeks old and has been a good, cooperative LST plant. She is on 20/4, and I use my PAR meter to calculate her uMols which are extrapolated out to give me her DLI you mentioned @Damien50 . I'm now focusing on letting her grow vertically since I have her horizontal shape wall to wall in the 2x2. Now she can reach for the stars - or in her case a HLG QB LED.

Its obvious y'all have the experience to know that 20/4 is a good lighting pattern from start to finish. With that said, I'll leave her be for her bud development phase. First auto, but all good growing basics apply regardless. Good nutes, proper ph, well managed lighting is essential.

BTW, @Damien50, your plants in the journal you linked are gorgeous. What a grow my friend....WOW!

From my experience with autos, how you care for the plant and maintain the environment will determine your yield unlike photos that have to be on a 12/12 down to a 10/14 schedule. I'll probably say this wrong but because of the ruderalis they have their own internal clock that isn't dependent on light schedule. As long as you're giving them enough light, look up DLI, I can't imagine that your light cycle matters as much.

DLI in the simplest way I can explain it refers to how many umols of light in a given cycle the plant needs.

There is 2 problems, what is optimal in MOL and what spectrum provides that optimal number?
Some light manufactures imply they have some knowledge, like Osram/Fluence, Lumi, etc., but of course it is proprietary for commercial reasons haha, there is no real scientific knowledge available anywhere as far as I know, just a lot of this or that many Mol seems to work very well and such.

I have an Apogee MQ-500 and imo this is the lowest entry point to PAR measurements. I also have 3 lightscouts to measure an approximate DLI.
But what you really want is probably an Asentek lightning passport for ease of use lol https://www.lightingpassport.com/# or some similar spectrometer

The Apogee will give an idea, but unless one has a test stand, it's pretty useless for specifics, moving the sensor just a fraction or changing the angle will make a big difference in measured value, AND where exactly to measure.

Perhaps the breeders should include recommended DLI numbers with specific spectral curves for start-mid-end vegging and flowering hahaha, especially for strains where the beans cost more than a fiver a pop lol, heck, throw in the flushing period too for those who cling on to myths

My Apogee and lightscouts are hardly ever used, the novelty wore off quickly and the futility took over. This is not a backyard one man two handed job, something more elaborate is required.

And yes, mobile phone sensors aren't gonna cut it

Just be aware before you decide to splash any cash, it ain't cheap gear and it ain't as simple as measuring the temperature!

I think @Tony21 provided a pretty detailed answer. I bought an Apogee PAR USB sensor that I use with my laptop and it plugs into the USB port. An app is available from Apogee and this is pretty cool to use overall. It is around $300 on Amazon, and I consider my purchase one that I really use and learn from. To me, this was money well spent.

My HLG LED QB has an adjustable power driver, so this PAR sensor helps me to dial in the light's output in a better way than simply "eyeballing" it. One of the advantages of LST or SCROG in a plant is that our goal is to develop a balanced canopy for light utilization. If a plant has a "pineapple" cola, the light's fall off to the lower bud sites is amazing when checked with a PAR meter.

Based on a 20 hour day, I set my uMol to give me 37.5 Mols of light for my DLI. This is my first auto grow, so I am keeping a notebook of how many Mols I am delivering and how this will impact my overall yield. If I raise my output to say 40 Mol on my next grow and keep all other factors consistent, I'll begin to find the sweet spot in my lighting curve....at least this is my logic.

What you say, spot on. If you can maintain close to similar conditions and keep up lab quality measurements and records and do this with a decent sample population and repeat it 4-5 times, yeah, for that strain a pattern will probably emerge, say a couple of years!

Some of the latest controllers works on a DLI setting, very useful to optimize power consumption, but how and if it applies to canna across strains is up for grabs, throw in photo and auto differences for good measure, and it's a long winding road.

Ideally I would like to fill up my plants DLI tank in a couple of hours or so, then go fishing the rest of the day, but those happy days will probably not come until I'm busy pushing daisies haha